The present invention relates generally, to a display unit including light emitting devices arrayed in such a manner as to be spaced from each other and, more particularly, to a display unit in which a light emission region of each of the light emitting devices is enlarged by giving a light diffusion function to a sealing material for covering the light emitting devices.
The assembly of an image display unit by arraying light emitting devices in a matrix is performed in two manners. For a liquid crystal display (LCD) or a plasma display panel (PDP), the light emitting devices are directly formed on a substrate, and for a light emitting diode display (LED display), single LED packages are arrayed on a substrate. In particular, for an image display unit such as an LCD or PDP, device isolation cannot be performed. Accordingly, in general, at the beginning of the production process, devices are formed in such a manner as to be spaced from each other with a pitch equivalent to a pixel pitch of the image display unit.
On the other hand, for an image display unit such as an LED display, LED chips are packaged by taking out LED chips after dicing, and individually connecting the LED chips to external electrodes by wire-bonding or bump-connection using flip-chip. In this case, before or after packaging, the LED chips are arrayed with a pixel pitch of the image display unit. However, such a pixel pitch is independent from an array pitch of the devices at the time of formation of the devices.
Since an LED (Light Emitting Diode) as a light emitting device is expensive, an image display unit using such LEDs can be produced at a low cost by producing a large number of LED chips from one wafer. Specifically, the cost of an image display unit can be lowered by reducing the size of an LED chip from an ordinary size, about 300 μm square to several ten μm square, and producing an image display unit by connecting such small-sized LED chips to each other. From this viewpoint, various techniques are known of forming devices at a high density, and transferring the devices to a wide region in such a manner that the devices are enlargedly spaced from each other, to produce a relatively large display unit such as an image display unit. For example, U.S. Pat. No. 5,438,241 discloses a thin film transfer method, and Japanese Patent Laid-open No. Hei 11-142878 discloses a method of forming a transistor array panel for display.
It should be noted, in the above-described display unit in which light emitting diodes are arrayed in such a manner as to be spaced from each other, since a light emission region of each of the light emitting devices forming pixels is significantly smaller than an array pitch of the light emitting devices, the light emission devices become conspicuous as luminous spots on a screen, thereby causing a problem in significantly degrading the image quality. Even if an average brightness over the screen has a suitable value, each light emitting diodes having a small-size glares as a luminous spot on the screen, thereby failing to obtain an image display excellent in viewability.